This invention relates to an audio signal transmission circuit, and, more particularly, to an audio signal transmission circuit comprising an input terminal, an output terminal, a volume control circuit and a tone control circuit both connected between the input and output terminals, and a record terminal from which is derived a substantially constant level tone-controlled audio signal to be recorded on a recording medium such as a magnetic tape by a suitable recorder.
An example of prior art audio signal transmission circuits provided with a record terminal is shown in FIG. 1. In this circuit, input signals of different levels from signal sources such as a disc record player, an FM tuner and so on are led to an input selecting switch 1, a variable attenuator (i.e. volume controller) 2, a tone control circuit 3, a main amplifier 4 and finally a loudspeaker 5. A record terminal 6 is provided at the output of the tone control circuit 3, and from this terminal a tone-controlled audio signal to be recorded is obtained. However, since the variable attenuator 2 is connected to the input of the tone control circuit 3, the level of a signal obtained at the record terminal 6 will inevitably change if the output level at the loudspeaker 5 is adjusted by means of the variable attenuator 2. It is, however, preferred that the level of a record signal should be changed only at a tape recorder. If the record terminal 6 is connected to the input of the variable attenuator 2 as indicated by a dotted line, the level of a record signal will not change even if the output level of the loudspeaker 5 is adjusted. In this case, however, the tone-controlled audio signal is never obtained at the record terminal 6. If an audio signal is to be recorded on a magnetic tape while being monitored by the loudspeaker, it is desired that the record signal should have the same tone quality as that of audio signal being reproduced by the loudspeaker.